main.rb

require 'myclass'

traceable = MyClass.CreateTraceableObject()

myclass.rb

require 'traceable_object'

class MyClass

  def self.CreateTracableObject
    obj = MyClass.new
    if APP_TRACE
      return TraceableObject.new(obj)
    else
      return obj
    end
  end
end

traceable_object.rb

class TraceableObject
  def initialize(obj)
    @obj = obj
  end

  def before_trace

  end

  def after_trace

  end

  def method_missing(sym, *args, &block)
    before_trace
    @obj.send sym, *args, &block
    after_trace
  end
end